1. Field of the Invention
The present invention generally relates to sterilization processes, and more particularly, to the techniques for monitoring the efficacy of a container system.
2. Description of the Related Art
A sterilization process generally involves in exposing the articles to be sterilized to a sterilizing medium that can kill bacterial microorganisms. Such processes are performed in sterilization chambers. The articles to be sterilized are often delivered to the sterilization chambers within a sterilization container in which the articles are both sterilized and subsequently stored in their sterilized state. In some instances, articles are merely disinfected, but are often nevertheless delivered within a container.
The containers are generally permeable to a sterilizing medium so that the sterilizing medium may enter the container during the sterilization process. A sterilizing medium may be a sterilant gas or vapor (e.g., hydrogen peroxide vapor) released by a sterilant source which is placed into or delivered into the sterilization container. As used hereinafter, the terms "gas" and "vapor" are used interchangeably. Such gas permeable containers may, for example, include pouches made of gas permeable materials or rigid trays wrapped with gas permeable wraps. In fact, a sterilization container may be configured as a sealable rigid container having ports to deliver a sterilant after the container has been sealed. In all above examples, however, the sterilization containers prevent the entry of the microorganisms into the container and thereby maintain the sterilized state of the articles therein.
In modem medical and dental practice, it is important to monitor the efficacy of the sterilization processes. That is, at the end of the sterilization cycle, it must be verified that all of the articles have been adequately exposed to the sterilizing medium and the existing microorganisms have been killed. Conventional sterilization processes commonly have two underlying monitoring devices that address such concerns, namely, biological indicators and chemical indicators. A biological indicator (BI) is a type of device having a source of microorganisms. In this context, the source of microorganisms refers to a predetermined concentration of microorganisms which are generally impregnated into a paper strip. A biological indicator is used to monitor the sterilization process and determine whether the particular sterilant succeeded in killing all the microorganisms in the load to be sterilized. In practice, the biological indicator is maintained in a gas permeable pack which is made of gas permeable materials. During the sterilization process, the biological indicators are conventionally placed outside the sterilization containers so that the biological indicator can be retrieved without compromising the sterility of the devices within the container. After exposure to the sterilization process, the source of microorganisms is placed in a sterile culture medium and incubated for a pre-determined period of time. Any surviving microorganisms indicates the incompleteness of the sterilization process in the container. One example of such a BI is shown in the Smith, U.S. Pat. No. 5,552,320, issued Sep. 3, 1996, incorporated herein by reference. Alternatively, a source of enzymes which mimic the response of living organisms to the sterilization procedure in a measurable fashion may be substituted for living microorganisms. Examples of this type of BI are shown in the Matner, U.S. Pat. No. 5,073,488 issued Dec. 17, 1991 and the Burnham, U.S. Pat. No. 5,486,459, issued Jan. 23, 1996, each of which are incorporated herein by reference.
On the other hand, chemical indicators (CI) are devices that primarily indicates whether or not the sterilization process cycle is carried out properly to deliver the sterilant to the sterilization chamber. Thus, chemical indicators do not provide a true indication that sterility has been achieved. Chemical indicators contain specific chemical compositions which chemically reacts and change color when exposed to the sterilizing medium. Additionally, chemical indicators may be designed to include and respond to a plurality of sterilization process parameters. For example, a chemical indicator can be designed to indicate or respond to certain sterilant concentrations, humidity, time, temperature, sterilant's pH or pressure.
During conventional sterilization processes, biological and chemical indicators are typically placed outside the gas permeable sterilization containers in which the load of the articles to be sterilized are placed. Upon completion of the sterilization process, containers, which are in their sealed state and with a presumably sterilized load, are often stored for a period of time before the sterilized articles are needed. In such conventional processes, the actual state of the sterilization inside the container is determined by inspecting the indicators located outside the container to determine whether the sterilization has been achieved. However, in practice, this approach has serious drawbacks because these indicators cannot provide accurate information about the sterilization status of the articles in the container. Since the indicators only display the outside readings, there is no way of knowing whether sterilization has occurred inside the container.
An alternative approach utilizes two chemical indicators to overcome the above given drawback. In this approach one of the chemical indicators is placed into the container adjacent to the load of articles. Unfortunately, the problem with this approach is that the actual state of the sterilization can only be determined by opening the container and inspecting the chemical indicator placed inside the container. However, this is also not practical and disturbs the sealed state of the container and the sterility of the devices therein. There also is a possibility that sterilization conditions were not achieved inside the container. Accordingly, throughout the storage period, the actual state of the sterilization process cannot be known.
Some container systems have a clear barrier through which a chemical indicator, but not a biological indicator, can be read. However, such chemical indicators cannot be removed without breaking the barrier. Moreover, in such a system, the chemical indicator is included within the load, so it is exposed to sterilant at the same time as the load. As a result, the chemical indicator may indicate a sterile result, even when portions of the load have not been exposed to sufficient sterilant to achieve sterility.
In view of the foregoing, there is a need for a new monitoring system for sterilization processes which is capable of indicating the state of the sterilization in an enclosed sterilization container while maintaining the sealed state of the sterilization container.